Telephone switchboard



Nov. 28., 1939. G. H. PETERSON TELEPHONE SWITCHBOARD Filed June 16, 1938Patented Nov. 2s, 1939 iJNITED STATES iastate vATENT orrice TELEPHONESWTCHBOARD Application June 16, 1938, Serial No. 214,078

4 Claims.

This invention relates to telephone systems and more particularly tomanually operated multiple switchboard systems for interconnecting linesof like or unlike character.

United States Patent 1,903,998 to R. W. Harper, discloses a universalcord circuit for indiscriminately interconnecting common battery andmagneto (local battery) lines in which the multiple jacks of the commonbattery lines are so arranged that when one of them is plugged into allof the jack sleeves of that line are grounded. The magneto line jacks,however, are not so arranged, the sleeves merely being connectedtogether, thus when one end of the cord is connected to a magneto linejack, all the jack sleeves of that line are at battery potential.

The principal feature of the Harper patent is a test circuit associatedwith the cord and operators telephone circuit whereby a click is heardin the operators telephone if the tip of a testing plug is brought intocontact with the sleeve of a busy line, either common battery ormagneto, in other words the test circuit being so arranged thatregardless of whether the tip or" the testing plug is brought intocontact with battery or ground a click will be heard by the operator asan indication that the line is busy. In some cases it may be desirableto make the subscriber lines of an associateddial exchange available tothe switchboard operator by bridging each dial line with a connection`which terminates in multiple jacks at the switchboard, along with thebeforementioned magneto lines, toll lines, etc., thus providingfacilities for enabling quick interconnecticn between rural and tolllines and dial subscriber in the same exchange area. Due to the factthat the sleeve circuits of dial subscribers lines are normally atbattery potential, the sleeves of such lines when multipled at theswitchboard, present a battery condition and in order to enable suchlines to function properly with cord circuits of the type shown in theHarper patent, it is necessary to modify the cord circuit so that nobusy indication will be given if the tip of a 1 testing cord is broughtinto contact with the sleeve of an idle line. When this is done,however, a busy rural line multiple as indicated by jacks 105 and M5 ofthe above patent will test idle, although busy, dueto the fact that thecord circuit, as now modiied, does not recognize battery potential as abusy condition and some means must be devised to cause the rural linemultiple to present the same busy condition as the other lines appearingat the switchboard.

An object of the invention is to operatively in- (Cl. 179-52l terconnectdial and manual common battery or rural subscribers lines by means ofuniversal manual switchboard cord circuits.

A feature of the invention whereby the above object is attained residesin so arranging the multiple jacks of rural and toll lines that when acord circuit plug is inserted in one of the jacks, ground will beconnected to all the sleeves of the other multiple jacks oi the line,but not to the sleeve of the jack in which the plug is inserted.

The .invention will be understood from the following descripton whenread in connection with the accompanying drawing, in which C is aswitchboard universal cord circuit identical with the cord circuitdisclosed in United States Patent 1,903,998 to R. W. Harper except forthe omission oi" means (relay I for connecting ground to a pointintermediate retardation coils |38 and 639, resistance i22 and condenser24.

A and B are common battery subscribers lines 20 identical with the linesof stations A and B shown in the Harper Patent 1,903,998, M and M' aremagneto or local battery subscribers lines whose multiple jacks arearranged in accordance with the present invention, X is the inward endof 2,3 a dial orlice Zero level trunk for incoming calls from dialsubscribers, and Y is a line circuit connected in multiple with a dialsubscribers line for outgoing calls.

As described in the Harper Patent 1,903,998 the jacks 00 and 426 arearranged with auxiliary contacts l2? and 928, and jacks mi' and M4 withsimilar unnumbered contacts, so that when a plug is inserted in any jackof any one of these lines all the jacks sleeves oi that line, includingthe sleeve of the jack plugged into, are grounded. This arrangementmakes all the vacant jacks of the line test-busy and operates the sleeverelay |09 in the cord circuit to supply talking battery to the line.

With respect to the incoming line X from the dial office it is'necessary that the sleeve circuit be connected either to battery orground as a relay therein, I'H, must be operated, in a wellknown manner,when the operator inserts a plug in one of the jacks, in order toextinguish the line lamp, release the line relay, and hold theconnection.

As this is a common battery line which functions in the same manner withrespect to the 0 cord circuit as the common battery subscribers lines Aand B, the jacks E50 and l5| are arranged with auxiliary contacts 54 and155 in the same manner as jacks |00, H26, |04 and M4, and the sleevecut-ofi relay I 1I is connected to battery 55 whereby the insertion of aplug (|01) in either jack will ground the sleeve circuit of both theline and cord thereby operating both sleeve relays |1| and |09.

Since the outgoing line Y, terminating in multiple jacks |52 and |53, isconnected in multiple with a dial subscribers line circuit, the sleeveconductor of which is connected to battery through the usual cut-01Trelay, and the sleeve of the operators cord circuit is also at batterypotential, through the usual cord sleeve relay, it is obviouslynecessary that the sleeve of the jack be grounded when the cord circuitis connected to it in order to operate the cut-off relay in thesubscribers line circuit at the dial oflice and also to operate thesleeve relay in the cord, and further, as the sleeves of both jacks areat battery potential when idle, the busy-test circuit of the cord, asdescribed in the Harper patent, must be modified in order that it willnot give a busy indication if the tip of the plug encounters batterypotential on one of the jack sleeves which is accomplished in a mannerheretofore described, i. e.,` by omitting a ground connection, when theoperators transmitter ||8 is in the jack, at the point |10 intermediatethe retard coils |38, |39, condenser |213 and resistance |22, originallyshown and described in Patent 1,903,998, and consequently, in order tomake the vacant multiple jacks of a busy line testbusy they must also begrounded when a plug is connected to the line. This is accomplished inthe same manner as in the case of jacks |26, |00, |06 and |49, i. e., byproviding auxiliary contacts |56 and |51, one on each jack, which areclosed when a plug is inserted, thereby connecting ground to both thesleeve of the jack plugged into and also the sleeves of all the othermultiple jacks associated with this line.

By arranging the jacks of lines A, B, X and Y in the manner described,proper operation of the cord and line circuits will follow when the cordis connected to any one of the respective jacks.

It will be noted that a grounded jack sleeve is a busy indication towhich the operators busy test circuit of the cord responds as fullydescribed in the Harper patent heretofore mentioned.

It is also assumed that there is still another type of line terminatingat the switchboard, i. e., magneto or local battery lines M and M'.These lines, due to the fact that the stations furnish their own talkingbattery, require a different cord circuit condition than the lines A, B,X and Y which receive their talking battery from the cord circuit andwhereas, when the cord is connected to any of the lines A, B, X or Y,the cord sleeve is grounded by the jack sleeves to operate therespective cord sleeve relays |09 and ||0 to supply talking battery tothe line, when the cord is connected to one of the lines M or M notalking battery is required and consequently the sleeves of the linemust be freed of ground in order not toroperate the cord sleeve relay.I-Iowever, when the cord is connected to a magneto line jack the othermultiple jacks of the line must test busy, i. e., must be grounded,which is the condition before determined by the lines A, B, X and Y.Hence, the insertion of a cord circuit plug |01 or |08 in a jack |58,|59, |60 or |6| of either line M or M must cause all the jack sleeves ofthat line, except the sleeve of the 'jack plugged into, to be grounded.This is accomplished in accordance with the present invention byarranging the jacks with auxiliary make contacts |62, |63, |64 and |65and break contacts |66, |61, |68 and |69 so that the insertion of a plugin any jack, for example |60, will open the normally closed contact |68thereby isolating the sleeve of that jack from the other jack sleeves ofthat line (M) and will close contact Ill thereby connecting ground tothe sleeve of jack |6| by way of the contacts |69 of that jack, whichcontacts remain closed.

From the foregoing it will be understood how a uniform busy conditioncan be applied to magneto rural or toll lines, manual common batterylines, multiples of dial subscribers lines, and zero level trunks fromdial equipment which terminate at a switchboard for indiscriminateinterconnection by a universal cord circuit of the type disclosed inPatent 1,903,998.

What is claimed is:

1. In a busy test system, a telephone switchboard, lines terminating inmultiple jacks at the switchboard, a cord circuit arranged for testingthe busy condition of and for interconnecting said lines, a source ofbusy potential, and means responsive to the connection of said cordcircuit to a jack of one of said lines to connect said source to thesleeves of all the jacks of that line except the sleeve of the jack towhich the cord is connected.

2. In a multiple switchboard busy test system, a cord circuitterminating in a plug, a plurality of multiple connected jacks eachhaving a sleeve element, a `source of test potential, and meansassociated with each jack responsive to insertion of said plug thereinto connect said source of test potential to all the multiple sleeveelements except the sleeve element of the jack in which the plug isinserted.

3. In a multiple switchboard system, a plug andv a plurality of multipleconnected jacks each having a sleeve element, and means associated witheach jack responsive to insertion of the.

plugv therein to connect ground to all the multiple sleeve elementsexcept the sleeve element of the jack in which the plug is inserted.

4. In a busy test system a telephone switchboard, common batterysubscribers lines terminating in multiple jacks at the switchboard,local battery lines also terminating in multiple jacks at the sameswitchboard, a universal cord circuit thereat for connecting to any ofsaid lines and normally conditioned vfor operation with local batterylines, an operators receiver adapted to be associated with said cord,means for energizing said receiver whenthe tip conductor of anassociated cord is connected to ground, means responsive to theconnection of said cord to a common battery line jack to connect groundto all the multiple sleeves of that line, including the sleeve of thejack with which the cord is connected, means controlled over the sleeveof said cord responsive to ground on the jack sleeve to condition thecord for common battery operation, and means responsive to connection ofsaid cord to a local battery line jack to ground all the multiple jacksleeves of that line except the sleeve of the jack with which the cordis connected.

GEORGE HARRY PETERSON.

